Often, severe pain or damage to the nervous system is caused by spinal abnormalities. Also, movement of the spinal column may be significantly limited by such abnormalities. Many of these abnormalities may be the result of, for example, trauma or degenerative disc disease. Known treatments of such abnormalities typically involve affixing screws or hooks to one or more vertebrae and connecting the screws or hooks to a rod that is aligned with the longitudinal axis of the spinal column to immobilize the spinal segments with respect to each other. Pedicle screw systems are frequently used to provide spinal fixation.
A number of pedicle screw systems are known, which share common techniques and principles of screw placement and rod attachment. Generally, bone screws are screwed into pedicles of vertebrae and coupled to at least one elongated rod. The pedicles, which consist of a strong shell of cortical bone and a core of cancellous bone, are generally used for the bone screw sites because they provide the strongest point of attachment of a spine and, thereby, the greatest resistance against bone-metal junction failure. The bone screws may be positioned so as to traverse all three columns of the vertebrae, thereby providing ventral and dorsal stability in the spine.
Known pedicle screw systems typically include pedicle screws and rods to stabilize adjacent spinal segments. Such systems also include variable angled coupling caps (or heads) on the pedicle screws to allow for angular adjustment of the coupling mechanism between the rod and screws. Since pedicle size and angulation varies throughout the spinal column, several different sizes and shapes of pedicle screws are used in these systems. These systems are generally designed to provide stable and rigid structures to promote bone growth and fusion.
Recovery from spinal surgery is typically a long and arduous process that places severe restrictions on patient mobility. Accordingly, a continuing need exists for systems and methodologies that improve patient recovery and reduce recovery time after surgery.